I have the new SR MacBook and also had the previous refresh for a few weeks. I can't say for certain but the SR MacBook seems to run slightly cooler than the last model. It's only slightly warm on the bottom when i'm just relaxing on my couch and it's in my lap.. I only do some light video watching/web surfing.. And seeing that the new MacBooks seem to run over 4 hours on a single charge tells me that this is achieved probably by a cooler running cpu/components.
Jay